;; biff
(defvar foundnewmbox "")
(defun fmbiff ()
  (interactive)
  (save-excursion
    (set-buffer "*Group*")
    (beginning-of-buffer)
    (defvar foundanymbox nil)
    (cond ((re-search-forward "INBOX.ALL" nil t)
           (setq foundanymbox t))
          (t (setq foundanymbox nil)))
    (set-buffer "*Group*")
    (beginning-of-buffer)
    (cond ((re-search-forward "0: INBOX.ALL" nil t)
           (setq foundnewmbox ""))
          (t (if foundanymbox (setq foundnewmbox "[M]")
               (setq foundnewmbox ""))))))

(unless (member 'foundnewmbox global-mode-string)
   (setq global-mode-string (append global-mode-string
                                    (list 'foundnewmbox))))

(add-hook 'gnus-after-getting-new-news-hook 'fmbiff)
(add-hook 'gnus-group-mode-hook 'fmbiff)

;; some shortcuts
(global-set-key (kbd "C-c i") 'fmbiff)